A Scientist, His Work and a Climate Reckoning
KEEPING WATCH The Mauna Loa Observatory,
at an altitude of 11,135 feet above sea level in
Hawaii, has been continuously monitoring and
collecting data related to climate change since
the 1950s. Jonathan Kingston/Aurora Select, for
The New York Times
By JUSTIN GILLIS
Published: December 21, 2010
MAUNA LOA OBSERVATORY, Hawaii - Two gray machines
sit inside a pair of utilitarian buildings here,
sniffing the fresh breezes that blow across
thousands of miles of ocean.
THE KEELINGS Charles D. Keeling with his
son Ralph in 1989. Scripps Institution of
Oceanography; U.C. San Diego
They make no noise. But once an hour, they spit
out a number, and for decades, it has been rising
The first machine of this type was installed on
Mauna Loa in the 1950s at the behest of Charles
David Keeling, a scientist from San Diego. His
resulting discovery, of the increasing level of
carbon dioxide in the atmosphere, transformed the
scientific understanding of humanity's
relationship with the earth. A graph of his
findings is inscribed on a wall in Washington as
one of the great achievements of modern science.
Yet, five years after Dr. Keeling's death, his
discovery is a focus not of celebration but of
conflict. It has become the touchstone of a
worldwide political debate over global warming.
When Dr. Keeling, as a young researcher, became
the first person in the world to develop an
accurate technique for measuring carbon dioxide
in the air, the amount he discovered was 310
parts per million. That means every million pints
of air, for example, contained 310 pints of
By 2005, the year he died, the number had risen
to 380 parts per million. Sometime in the next
few years it is expected to pass 400. Without
stronger action to limit emissions, the number
could pass 560 before the end of the century,
double what it was before the Industrial
The greatest question in climate science is: What
will that do to the temperature of the earth?
Scientists have long known that carbon dioxide
traps heat at the surface of the planet. They
cite growing evidence that the inexorable rise of
the gas is altering the climate in ways that
threaten human welfare.
Fossil fuel emissions, they say, are like a
runaway train, hurtling the world's citizens
toward a stone wall - a carbon dioxide level
that, over time, will cause profound changes.
The risks include melting ice sheets, rising
seas, more droughts and heat waves, more flash
floods, worse storms, extinction of many plants
and animals, depletion of sea life and - perhaps
most important - difficulty in producing an
adequate supply of food. Many of these changes
are taking place at a modest level already, the
scientists say, but are expected to intensify.
Reacting to such warnings, President George Bush
committed the United States in 1992 to limiting
its emissions of greenhouse gases, especially
carbon dioxide. Scores of other nations made the
same pledge, in a treaty that was long on
promises and short on specifics.
But in 1998, when it came time to commit to
details in a document known as the Kyoto
Protocol, Congress balked. Many countries did
ratify the protocol, but it had only a limited
effect, and the past decade has seen little
additional progress in controlling emissions.
Many countries are reluctant to commit themselves
to tough emission limits, fearing that doing so
will hurt economic growth. International climate
talks in Cancún, Mexico, this month ended with
only modest progress. The Obama administration,
which came into office pledging to limit
emissions in the United States, scaled back its
ambitions after climate and energy legislation
died in the Senate this year.
Challengers have mounted a vigorous assault on
the science of climate change. Polls indicate
that the public has grown more doubtful about
that science. Some of the Republicans who will
take control of the House of Representatives in
January have promised to subject climate
researchers to a season of new scrutiny.
One of them is Representative Dana Rohrabacher,
Republican of California. In a recent
Congressional hearing on global warming, he said,
"The CO2 levels in the atmosphere are rather
But most scientists trained in the physics of the
atmosphere have a different reaction to the
"I find it shocking," said Pieter P. Tans, who
runs the government monitoring program of which
the Mauna Loa Observatory is a part. "We really
are in a predicament here, and it's getting worse
As the political debate drags on, the mute gray
boxes atop Mauna Loa keep spitting out their
numbers, providing a reality check: not only is
the carbon dioxide level rising relentlessly, but
the pace of that rise is accelerating over time.
"Nature doesn't care how hard we tried," Jeffrey
D. Sachs, the Columbia University economist, said
at a recent seminar. "Nature cares how high the
parts per million mount. This is running away."
A Passion for Precision
Perhaps the biggest reason the world learned of
the risk of global warming was the unusual
personality of a single American scientist.
Charles David Keeling's son Ralph remembers that
when he was a child, his family bought a new home
in Del Mar, Calif., north of San Diego. His
father assigned him the task of edging the lawn.
Dr. Keeling insisted that Ralph copy the habits
of the previous owner, an Englishman who had
taken pride in his garden, cutting a precise
two-inch strip between the sidewalk and the grass.
"It took a lot of work to maintain this
attractive gap," Ralph Keeling recalled, but he
said his father believed "that was just the right
way to do it, and if you didn't do that, you were
cutting corners. It was a moral breach."
Dr. Keeling was a punctilious man. It was by no
means his defining trait - relatives and
colleagues described a man who played a brilliant
piano, loved hiking mountains and might settle a
friendly argument at dinner by pulling an
etymological dictionary off the shelf.
But the essence of his scientific legacy was his
passion for doing things in a meticulous way. It
explains why, even as challengers try to pick
apart every other aspect of climate science, his
half-century record of carbon dioxide
measurements stands unchallenged.
By the 1950s, when Dr. Keeling was completing his
scientific training, scientists had been
observing the increasing use of fossil fuels and
wondering whether carbon dioxide in the air was
rising as a result. But nobody had been able to
take accurate measurements of the gas.
As a young researcher, Dr. Keeling built
instruments and developed techniques that allowed
him to achieve great precision in making such
measurements. Then he spent the rest of his life
applying his approach.
In his earliest measurements of the air, taken in
California and other parts of the West in the
mid-1950s, he found that the background level for
carbon dioxide was about 310 parts per million.
That discovery drew attention in Washington, and
Dr. Keeling soon found himself enjoying
government backing for his research. He joined
the staff of the Scripps Institution of
Oceanography, in the La Jolla section of San
Diego, under the guidance of an esteemed
scientist named Roger Revelle, and began laying
plans to measure carbon dioxide around the world.
Some of the most important data came from an
analyzer he placed in a government geophysical
observatory that had been set up a few years
earlier in a remote location: near the top of
Mauna Loa, one of the volcanoes that loom over
the Big Island of Hawaii.
He quickly made profound discoveries. One was
that carbon dioxide oscillated slightly according
to the seasons. Dr. Keeling realized the reason:
most of the world's land is in the Northern
Hemisphere, and plants there were taking up
carbon dioxide as they sprouted leaves and grew
over the summer, then shedding it as the leaves
died and decayed in the winter.
He had discovered that the earth itself was breathing.
A more ominous finding was that each year, the
peak level was a little higher than the year
before. Carbon dioxide was indeed rising, and
quickly. That finding electrified the small
community of scientists who understood its
implications. Later chemical tests, by Dr.
Keeling and others, proved that the increase was
due to the combustion of fossil fuels.
The graph showing rising carbon dioxide levels
came to be known as the Keeling Curve. Many
Americans have never heard of it, but to
climatologists, it is the most recognizable
emblem of their science, engraved in bronze on a
building at Mauna Loa and carved into a wall at
the National Academy of Sciences in Washington.
By the late 1960s, a decade after Dr. Keeling
began his measurements, the trend of rising
carbon dioxide was undeniable, and scientists
began to warn of the potential for a big increase
in the temperature of the earth.
Dr. Keeling's mentor, Dr. Revelle, moved to
Harvard, where he lectured about the problem.
Among the students in the 1960s who first saw the
Keeling Curve displayed in Dr. Revelle's
classroom was a senator's son from Tennessee
named Albert Arnold Gore Jr., who marveled at
what it could mean for the future of the planet.
Throughout much of his career, Dr. Keeling was
cautious about interpreting his own measurements.
He left that to other people while he
concentrated on creating a record that would
John Chin, a retired technician in Hawaii who
worked closely with Dr. Keeling, recently
described the painstaking steps he took, at Dr.
Keeling's behest, to ensure accuracy. Many hours
were required every week just to be certain that
the instruments atop Mauna Loa had not drifted
out of kilter.
The golden rule was "no hanky-panky," Mr. Chin
recalled in an interview in Hilo, Hawaii. Dr.
Keeling and his aides scrutinized the records
closely, and if workers in Hawaii fell down on
the job, Mr. Chin said, they were likely to get a
call or letter: "What did you do? What happened
In later years, as the scientific evidence about
climate change grew, Dr. Keeling's
interpretations became bolder, and he began to
issue warnings. In an essay in 1998, he replied
to claims that global warming was a myth,
declaring that the real myth was that "natural
resources and the ability of the earth's
habitable regions to absorb the impacts of human
activities are limitless."
Still, by the time he died, global warming had
not become a major political issue. That changed
in 2006, when Mr. Gore's movie and book, both
titled "An Inconvenient Truth," brought the issue
to wider public attention. The Keeling Curve was
featured in both.
In 2007, a body appointed by the United Nations
declared that the scientific evidence that the
earth was warming had become unequivocal, and it
added that humans were almost certainly the main
cause. Mr. Gore and the panel jointly won the
Nobel Peace Prize.
But as action began to seem more likely, the
political debate intensified, with fossil-fuel
industries mobilizing to fight emission-curbing
measures. Climate-change contrarians increased
their attack on the science, taking advantage of
the Internet to distribute their views outside
the usual scientific channels.
In an interview in La Jolla, Dr. Keeling's widow,
Louise, said that if her husband had lived to see
the hardening of the political battle lines over
climate change, he would have been dismayed.
"He was a registered Republican," she said. "He
just didn't think of it as a political issue at
Not long ago, standing on a black volcanic plain
two miles above the Pacific Ocean, the director
of the Mauna Loa Observatory, John E. Barnes,
pointed toward a high metal tower.
Samples are taken by hoses that snake to the top
of the tower to ensure that only clean air is
analyzed, he explained. He described other
measures intended to guarantee an accurate
record. Then Dr. Barnes, who works for the
National Oceanic and Atmospheric Administration,
displayed the hourly calculation from one of the
It showed the amount of carbon dioxide that morning as 388 parts per
After Dr. Keeling had established the importance
of carbon dioxide measurements, the government
began making its own, in the early 1970s. Today,
a NOAA monitoring program and the Scripps
Institution of Oceanography program operate in
parallel at Mauna Loa and other sites, with each
record of measurements serving as a quality check
on the other.
The Scripps program is now run by Ralph Keeling,
who grew up to become a renowned atmospheric
scientist in his own right and then joined the
Scripps faculty. He took control of the
measurement program after his father's sudden
death from a heart attack.
In an interview on the Scripps campus in La
Jolla, Ralph Keeling calculated that the carbon
dioxide level at Mauna Loa was likely to surpass
400 by May 2014, a sort of odometer moment in
mankind's alteration of the atmosphere.
"We're going to race through 400 like we didn't
see it go by," Dr. Keeling said.
What do these numbers mean?
The basic physics of the atmosphere, worked out
more than a century ago, show that carbon dioxide
plays a powerful role in maintaining the earth's
climate. Even though the amount in the air is
tiny, the gas is so potent at trapping the sun's
heat that it effectively works as a one-way
blanket, letting visible light in but stopping
much of the resulting heat from escaping back to
Without any of the gas, the earth would most
likely be a frozen wasteland - according to a
recent study, its average temperature would be
colder by roughly 60 degrees Fahrenheit. But
scientists say humanity is now polluting the
atmosphere with too much of a good thing.
In recent years, researchers have been able to
put the Keeling measurements into a broader
context. Bubbles of ancient air trapped by
glaciers and ice sheets have been tested, and
they show that over the past 800,000 years, the
amount of carbon dioxide in the air oscillated
between roughly 200 and 300 parts per million.
Just before the Industrial Revolution, the level
was about 280 parts per million and had been
there for several thousand years.
That amount of the gas, in other words, produced
the equable climate in which human civilization
Other studies, covering many millions of years,
show a close association between carbon dioxide
and the temperature of the earth. The gas
seemingly played a major role in amplifying the
effects of the ice ages, which were caused by
wobbles in the earth's orbit.
The geologic record suggests that as the earth
began cooling, the amount of carbon dioxide fell,
probably because much of it got locked up in the
ocean, and that fall amplified the initial
cooling. Conversely, when the orbital wobble
caused the earth to begin warming, a great deal
of carbon dioxide escaped from the ocean,
amplifying the warming.
Richard B. Alley, a climate scientist at
Pennsylvania State University, refers to carbon
dioxide as the master control knob of the earth's
climate. He said that because the wobbles in the
earth's orbit were not, by themselves, big enough
to cause the large changes of the ice ages, the
situation made sense only when the amplification
from carbon dioxide was factored in.
"What the ice ages tell us is that our physical
understanding of CO2 explains what happened and
nothing else does," Dr. Alley said. "The ice ages
are a very strong test of whether we've got it
When people began burning substantial amounts of
coal and oil in the 19th century, the carbon
dioxide level began to rise. It is now about 40
percent higher than before the Industrial
Revolution, and humans have put half the extra
gas into the air since just the late 1970s.
Emissions are rising so rapidly that some experts
fear that the amount of the gas could double or
triple before emissions are brought under control.
The earth's history offers no exact parallel to
the human combustion of fossil fuels, so
scientists have struggled to calculate the effect.
Their best estimate is that if the amount of
carbon dioxide doubles, the temperature of the
earth will rise about five or six degrees
Fahrenheit. While that may sound small given the
daily and seasonal variations in the weather, the
number represents an annual global average, and
therefore an immense addition of heat to the
The warming would be higher over land, and it
would be greatly amplified at the poles, where a
considerable amount of ice might melt, raising
sea levels. The deep ocean would also absorb a
tremendous amount of heat.
Moreover, scientists say that an increase of five
or six degrees is a mildly optimistic outlook.
They cannot rule out an increase as high as 18
degrees Fahrenheit, which would transform the
Climate-change contrarians do not accept these numbers.
The Internet has given rise to a vocal cadre of
challengers who question every aspect of the
science - even the physics, worked out in the
19th century, that shows that carbon dioxide
traps heat. That is a point so elementary and
well-established that demonstrations of it are
routinely carried out by high school students.
However, the contrarians who have most influenced
Congress are a handful of men trained in
atmospheric physics. They generally accept the
rising carbon dioxide numbers, they recognize
that the increase is caused by human activity,
and they acknowledge that the earth is warming in
But they doubt that it will warm nearly as much
as mainstream scientists say, arguing that the
increase is likely to be less than two degrees
Fahrenheit, a change they characterize as
Among the most prominent of these contrarians is
Richard Lindzen of the Massachusetts Institute of
Technology, who contends that as the earth
initially warms, cloud patterns will shift in a
way that should help to limit the heat buildup.
Most climate scientists contend that little
evidence supports this view, but Dr. Lindzen is
regularly consulted on Capitol Hill.
"I am quite willing to state," Dr. Lindzen said
in a speech this year, "that unprecedented
climate catastrophes are not on the horizon,
though in several thousand years we may return to
an ice age."
The Fuel of Civilization
While the world's governments have largely
accepted the science of climate change, their
efforts to bring emissions under control are
The simple reason is that modern civilization is
built on burning fossil fuels. Cars, trucks,
power plants, steel mills, farms, planes, cement
factories, home furnaces - virtually all of them
spew carbon dioxide or lesser heat-trapping gases
into the atmosphere.
Developed countries, especially the United
States, are largely responsible for the buildup
that has taken place since the Industrial
Revolution. They have begun to make some headway
on the problem, reducing the energy they use to
produce a given amount of economic output, with
some countries even managing to lower their total
But these modest efforts are being swamped by
rising energy use in developing countries like
China, India and Brazil. In those lands, economic
growth is not simply desirable - it is a moral
imperative, to lift more than a third of the
human race out of poverty. A recent scientific
paper referred to China's surge as "the biggest
transformation of human well-being the earth has
China's citizens, on average, still use less than
a third of the energy per person as Americans.
But with 1.3 billion people, four times as many
as the United States, China is so large and is
growing so quickly that it has surpassed the
United States to become the world's largest
overall user of energy.
Barring some big breakthrough in clean-energy
technology, this rapid growth in developing
countries threatens to make the emissions problem
Emissions dropped sharply in Western nations in
2009, during the recession that followed the
financial crisis, but that decrease was largely
offset by continued growth in the East. And for
2010, global emissions are projected to return to
the rapid growth of the past decade, rising more
than 3 percent a year.
Many countries have, in principle, embraced the
idea of trying to limit global warming to two
degrees Celsius, or 3.6 degrees Fahrenheit,
feeling that any greater warming would pose
unacceptable risks. As best scientists can
calculate, that means about one trillion tons of
carbon can be burned and the gases released into
the atmosphere before emissions need to fall to
"It took 250 years to burn the first
half-trillion tons," Myles R. Allen, a leading
British climate scientist, said in a briefing.
"On current trends, we'll burn the next
half-trillion in less than 40."
Unless more serious efforts to convert to a new
energy system begin soon, scientists argue, it
will be impossible to hit the 3.6-degree target,
and the risk will increase that global warming
could spiral out of control by century's end.
"We are quickly running out of time," said Josep
G. Canadell, an Australian scientist who tracks
In many countries, the United States and China
among them, a conversion of the energy system has
begun, with wind turbines and solar panels
sprouting across the landscape. But they generate
only a tiny fraction of all power, with much of
the world's electricity still coming from the
combustion of coal, the dirtiest fossil fuel.
With the exception of European countries, few
nations have been willing to raise the cost of
fossil fuels or set emissions caps as a way to
speed the transformation. In the United States, a
particular fear has been that a carbon policy
will hurt the country's industries as they
compete with companies abroad whose governments
have adopted no such policy.
As he watches these difficulties, Ralph Keeling
contemplates the unbending math of carbon dioxide
emissions first documented by his father more
than a half-century ago and wonders about the
future effects of that increase.
"When I go see things with my children, I let
them know they might not be around when they're
older," he said. " 'Go enjoy these beautiful
forests before they disappear. Go enjoy the
glaciers in these parks because they won't be
around.' It's basically taking note of what we
have, and appreciating it, and saying goodbye to
On Dec. 11, another round of international
climate negotiations, sponsored by the United
Nations, concluded in Cancún. As they have for 18
years running, the gathered nations pledged
renewed efforts. But they failed to agree on any
binding emission targets.
Late at night, as the delegates were wrapping up
in Mexico, the machines atop the volcano in the
middle of the Pacific Ocean issued their own
silent verdict on the world's efforts.
At midnight Mauna Loa time, the carbon dioxide level hit 390 - and rising.
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